docs: def on_sigchld(self, _signum, _unused_frame):
          """Invoked when a child sends up an SIGCHLD signal.
  
          :param int _signum: The signal that was invoked
          :param frame _unused_frame: The frame that was interrupted
  
          """
          LOGGER.info('SIGCHLD received from child')
          if not self.active_processes(False):
              LOGGER.info('Stopping with no active processes and child error')
              signal.setitimer(signal.ITIMER_REAL, 0, 0)
              self.set_state(self.STATE_STOPPED)